Sludge drying process and assembly keeps mixture below 65 per cent dry matter

摘要

A sludge drying process makes use of a fluidised bed drier or a drum drier, through which drying air is passed and then recirculated. Dust created in the sludge drying process is removed from the dried product, a sieved fine fraction or a sieved coarse fraction. The dust is returned as a mass and mixed in de-watered sludge mixture which is then surrendered to the main drier. The process comprises: (a) the dry content of the sludge mixture is kept at a level well below 65 %; (b) the fresh sludge not required for combination with dust is surrendered direct to the drier; (c) the returning mass flow of dust is measured, and the rate at which de-watered sludge which is also added, is varied accordingly; (d) the rate at which dust is returned, is measured using a weigh belt, an impulse quantity measuring device, or an impact panel measuring device; and (e) the coarse fraction is pulverised and then mixed in. Also claimed is a suitable assembly.